Chai with Mocha: Unit testing in Node.js

chai.js

//Chai Syntax
const expect = require('chai').expect;

describe("tests", () => {
    it("should be true", () => {
        const res = false;
        //some code
        expect(res).to.be.true; //will give a failing test(obviously)
    })
})

failing.js

//passing and failing tests
describe("mocha", () => {
    it("should have tests that pass", () => {
        //some code
    })
    it("should have tests that fail", () => {
        //some code
        throw new Error('Failed test');
    })
})

package.json

//can use the watch flag like this
"scripts": {
    "test": "mocha --watch"
  }
//or like this
"mocha": {
    "watch":true
  }
//or can make a separate file altogether and write the configurations in that

test.js

//Mocha Syntax
describe("arithmetic operations", () => {
    describe("add", () => {
        it("should give sum of two numbers", () => {
            //some code
        })
        it('should give sum of five numbers',() => {
            //some code
        })
    })
    describe("subtract", () => {
        it("should give the difference of two numbers", () => {
            //some code
        })
    })
})

testing.js

module.exports = {
    getSum: (n1,n2) => {
        return n1+n2;
    },

    isValidEmail: (email) => {
        let reg = /^\w*(\-\w)?(\.\w*)?@\w*(-\w*)?\.\w{2,3}(\.\w{2,3})?$/
        if (reg.test(email))
            return true;
        else 
            return false; 
    },

    getName: (email) => {
        const res = (email.split("@")[1] || '').split('.');
        return res[0];
    },

    getFactorial: (num) => {
        let res=1;
        
        while(num!=1)
        {
            res*=num;
            num--;
        }

        return res;

    }

}

testing.spec.js

const expect = require('chai').expect;
const {getName, getFactorial, isValidEmail, getSum} = require('./testing')

describe('testing', () => {

    describe('getSum', () => {
        it('should return the sum of two numbers', () => {
            const n1 = 5, n2 = 6;
            expect(getSum(n1,n2)).to.eq(11);
        })
    })
    
    describe('isValidEmail', () => {
        it('should be true if given a valid email',() => {
            const email = "anjali@mochajs.org";

            expect(isValidEmail(email)).to.be.true;
        })
    })
    
    describe('getName', () => {
        it('should give the name on receiving an email id', () => {
            const email = "anjali@mochajs.org";

            expect(getName(email)).to.eq('mochajs')
        })
    })
    describe('getFactorial', () => {
        it('should give factorial of the number provided', () => {
            const num = 3;

            expect(getFactorial(num)).to.eq(6)
        })
    })
})

Passing and Failing tests

Testing.spec.js result: